Sciencemadness Discussion Board

Blue color using copper II benzoate

jamit - 24-1-2012 at 21:16

I just made copper benzoate using copper sulfate and potassium benzoate. Filtered and washed with water, followed by 99% isopropyl alcohol and dried and powdered it. I then mixed one part copper benzoate with five parts ammonium perchlorate... Used mortar and pestle to finely ground it and set it on fire using a gas torch... The result was far from what I expected... There was no blue color whatsoever... Just yellow flames. There is no way there was any sodium ions present. Ammonium perchlorate was purchased from pyro supply. I thought copper benzoate produces blue color when mixed with ammonium perchlorate. The burn was very clean. Am I missing something? Can someone help me with this problem?

[Edited on 25-1-2012 by jamit]

Aqua_Fortis_100% - 24-1-2012 at 21:32

Im thinking in carbon burning (orange-yellow) from benzene ring on benzoate ruining your blue colour. Benzoates and other benzene ring containing substances are most suited to whistling compositions rather than colouring.. salts of benzoic, gallic and salicylic acid, etc are used.. Originally salts of picric acid were used too, but of course are too dangerous..

Did you used parts by weight?

Aditionally, although this may not be the case but.. Was CuSO4 and water used pure enough/sodium free?

EDIT: Ah, the problem of carbon containing compounds in colour comps apply to binders too. If a binder is required in such mixture, the minimum possible of it should be used since like said, carbon-containing compounds may be oxidized to the atomic carbon level in the flame and produce an orange-yellow color. Using a binder that is already (substantially) oxidized (one with a high oxygen content, such as dextrine) can minimize this problem. Binders such as paraffin that contain little or no oxygen should be avoided (unless a HOT, oxygen-rich composition is being prepared).

[Edited on 25-1-2012 by Aqua_Fortis_100%]

jamit - 24-1-2012 at 21:45

Thanks for your thoughts Aqua. Are you saying that ammonium perchlorate and copper benzoate are reacting to produce some form of carbon benzene... And contaminating the color? Have you done this reaction before or are you just speculating?

According to most pyro forums copper benzoate is used to produce blue color... My mixture wasn't even close so I'm missing something majorly.

Has anyone tried mixing ammonium perchlorate with copper benzoate? What color did it produce?

Aqua_Fortis_100% - 24-1-2012 at 22:27

Have you done this reaction before or are you just speculating?

I still dont have acess to NH4ClO4, but have to KClO3 and some good (but old) books on pyrotechnics. Ive made once a whistling composition made from copper terephthalate (a benzoate friend..but with more carbons - two fused benzene rings) and pure sodium-free KClO3 (yeah, is not recommended to mix chlorates and copper compounds, but I did make small amounts and didnt stored it, used it all after mixing). Yellow colour was observed (actually I cant prove that comes from sodium, carbon or both, since I made it just for whistling, not for colour... My terephthalate was made reacting hot strong NaOH solution with some small cut PET bottles with reflux, dilluting, reacting with HCl; the ppted terephthalic acid was then filtered, washed and re-dissolved in NaOH.. Then this solution was added to copper sulfate solution and the ppt filtered and well washed.. certainly it contained some sodium).

The book I was reading rather present copper (I) chloride (unstable when moist, though), copper carbonate, oxide, oxychloride, acetoarsenite(paris green), etc but I dont saw yet mention on copper benzoate, so probably Im 'phased out' haha.. (BTW, I was reading 'The Chemistry of Fireworks' written by Michael S. Russel).
Based on this, and on my little experience with whistle... Yes, you can told me Im just speculating. :D

According to most pyro forums copper benzoate is used to produce blue color... My mixture wasn't even close so I'm missing something majorly.

Since Im weak on pyro foruns, I didnt knew people used copper benzoate in colour comps, but if you said people are using it with sucess, then yes, you are missing something and my advise is probably not useful to solve your problem; sorry.

[Edited on 25-1-2012 by Aqua_Fortis_100%]

jamit - 24-1-2012 at 22:43

Aqua@ your attempt to help is much appreciated. Thanks. Something to think about. I'm open to all suggestions since I can't get it to work.

I have potassium perchlorate but I read that it works better with ap. I know someone on this forum has tried what I've done, so I'll just wait...and hope to hear from them.

[Edited on 25-1-2012 by jamit]

jamit - 25-1-2012 at 15:28

Has anyone with pyro eXperience tried getting blue color with copper benzoate and ammonium perchlorate?

I just mixed the two chemicals in 8:2 ratio but it's nothing like a neon blue. Is the exact composition important?

Mumbles - 26-1-2012 at 02:28

I've used copper benzoate prepared quite similarly to yours and successfully made decent blues. It wasn't as deep as I'd prefer, but it was definitely not yellow. It was prepared from food grade potassium benzoate and copper sulfate from pond treatments. The original formula given by Dave Blesser is 82:18, but that really should not matter. I've made Dave's formula, as well as a few purples that are floating about. Everything was screened together well, and bound into stars.

Out of curiosity, are you binding this at all, or burning it as a loose powder? Believe it or not, but binding into a compact shape has a big effect. I've always believed this sort of confines everything intimately and restricts the available atmospheric oxygen, but that's really just a lot of hand waving BS if you really want to get to real factors. The stars were originally bound with nitrocellulose solution, but I've seen them made them with +5% dextrin as well. Many times the color is good when bound, but washed out when burnt as a powder. I guess turning yellow indicating carbon burning in the flame envelope is an extreme form of being washed out.

If you want to differentiate carbon yellows from sodium yellows you may want to keep an eye out for cobalt glass. You can get sheets from ebay and some other scientific suppliers. It's also used to make blue glass bottles for perfume and other fanciful things. I had the plates, but the bottles probably wouldn't be a bad place to start at least. It fairly cleanly filters out yellows, of which sodium strongly emits in. This is total speculation, but if it's really coming from carbon, it may be possible to see some of the orange and reds and other colors of carbon.

jamit - 26-1-2012 at 04:04

Thanks Mumbles for sharing your experience on getting blue color with copper benzoate. I've been waiting for someone to answer my question(s)... someone who can speak about it based on personal experience. so thanks alot!

I burned the ap/copper benzoate mixture as a loose powder and that may have been my problem. Somehow, it won't produce any blue flames, although I did see some blue on the edges.

If I'm interpreting you correctly, I need to bind the ap/copper benzoate mixture, right?

Can I ask, what you mean by "binding"? Do you mean, wet the whole mixture of ap/copper benzoate with a binder like dextrin (5%) so that it can be molded, then put into a tube and ignited by a fuse?

I'm not much of a pyro guy but interested in making use of my copper benzoate. and yes I've read that the mixture is 82:18 ap/copper benzoate. :D

Maniak - 26-1-2012 at 04:28

This kind of pyrotechnics is not in my primary interest, but few years ago I made some copper benzoate and also tried it mixed with AP. I pressed it by 1 ton hydraulic press in 13 mm diameter steel matrix. Pressed composition produced nice blue flame with yellow border. I didn't try it in powdery state, but I believe that this can influence flame color a bit..

Mumbles - 26-1-2012 at 11:27

Without getting into the extreme details of this, yes, if you add dextrin and activate it with water it can be molded into shapes. When I did it, the composition was wetted with nitrocellulose solution, formed into a flat patty, and sliced into cubes. The same process can be used with dextrin. You want to get it about to the consistency of clay. A little more or a little less water and the "just right" state will become apparent with some experience. The other common way to make stars is to wet the composition and press or ram it into a tube, and eject. This will essentially make a large tablet or pellet. Copper, PVC, even disposable syringes are well suited to this when combined with even wooden dowels. For this you want to get the composition much less wet. You'd be looking at somewhere between 8-12% moisture probably. You could encase it into a tube as well. For that I'd recommend a fairly thin tube. Something even as simple as 2-3 turns of computer paper. You really don't even have to get it all that wet to do that method. Just press it down into the tube with a dowel or pen or something. I'd caution against this way to some degree however. The burning paper can impart a yellow tinge to the flame, which may be impossible to discern from the composition itself.

I can't promise binding will solve the problems, but it seems like a reasonable thing to try. It definitely should not be just yellow.

jamit - 26-1-2012 at 14:19

Thanks muMbles. I'll try that.

quicksilver - 26-1-2012 at 14:48

Blues ARE tough to get that are clean. Using Copper Benzoate, I imagine it's possible but it's not the strongest blue. I would start by cutting down a bit on the perchorate and making the composition very intimate. If they are not VERY fine and then mixed in a manner than will hold the composition together the chance of separation will ruin your efforts. Do NOT grind them together! Make each one as fine as possible and use a bonding element (dextrine). Adding additional blue-oriented composition may be a good idea but ammonium perchlorate is often a tough oxidizer to use for color change. And frankly has close to the same copper sensitivities that a chlorate has. Potassium perchlorate would be safer and easier all the way around. Personally, I would stay away from a copper and ammonium perchorate.

Realistically, it's not safe. An ammonium perchlorate rocket motor plant blew up from exposure to copper in the form of brass. I DO have some simple Blue color compositions that are safer. The intimacy would be achieved by using a SMALL amount of binder once the materials are sub-200 mesh. Never use friction or impact with a pyro composition with copper or copper salt W/ ammonium nitrate, ammonium perchorate, or chlorate.

This can get you a blue IF the charcoal is a gunpowder quality (high phenothalien) charcoal.

Charcoal (all equal weights)


However IF you really want a BLUE you're going to HAVE to provide a chlorine donor. Copper oxide or copper sulfate will provide some blue but never as much as a composition with a chlorine donor. That's the real bottom line.

[Edited on 26-1-2012 by quicksilver]

jamit - 26-1-2012 at 17:30

Thanks quicksilver! What chlorine donor would you recommend?
I have PVC or would you suggest something else?

Mumbles - 26-1-2012 at 19:46

I can give you all sorts of tried and tested blue formulas if you'd like. I personally don't like AP, and for the most part don't use it. It has too small of a flame, and is too prone to being blown out. Add in to this that I use chlorates occasionally, AP is pretty much banned from my shop. Ammonium perchlorate has the advantage however that it acts as a chlorine donor and oxidizer in formulas such as the one above. It's also pretty much indispensable for good colored strobes.

Quicksilver, if you're talking about the PEPCON explosion in Henderson, Nevada, that had absolutely nothing to do with copper in any meaningful way. It was not caused, nor exacerbated by copper or brass as far as the information available is concerned. Copper metal will certainly be corroded by most ammonium salts. I don't have my book or list of impact sensitivities but I actually don't recall common copper salts such as oxides, carbonates, etc being overly sensitive with chlorates. Certainly 150 years of history has shown they can be used safely together, especially once impure sulfur was eliminated.

jamit - 26-1-2012 at 20:37

Thanks mumbles!

Sure, I would appreciate it if you can give me some tried and tested blue formulas. Are there any that you can just lite using powdery mixture or do they all require binders?

quicksilver - 27-1-2012 at 09:00

Nope I don't think it was PEPCON. It was from a NOAA report:
[ASESB Expl. Report 211 1966]. "(Ammonium Perchlorate) can explode when mixed with sugar, charcoal or on contact with hot copper pipes." It may have been Kerr-McGee research after the PEPCON disaster (Kerr-McGee was located very close to PEPCON). However most any search on "Ammonium Perchlorate and copper" will show it's serious sensitivity. Expert witness testimony regarding copper / ammonium perc has been widely published via peer reviewed journals and I may had mistaken the PEPCON fuel/oxidizer mix tragedy for the Kerr-McGee report (1988?) after the fact re: copper exposure issue. So I did a quick search to make sure.
Published in CHEMICAL ENGINEERING PROGRESS, September 1957 (Vol. 53, No. 9) was some of that material:

(Metallic [Cu] contamination increases the sen­sitivity of ammonium perchlorate (i.e., certain metallic perchlorates are extremely sensitive).


Personally, I agree w/ Mumbles that Ammonium perchlorate had been known as a chlorine donor of sorts. but I think it's a better idea to use something other (PVC, Parlon, whatever). Some of the deepest blues I have seen were from materials that are not too easy to get or are really toxic (Hg salts, Paris Green) but the one thing they all had in common was a quality chlorine donor & care taken to not "wash out" the color with too high a percentage "non-color oxidizer". This may be one reason why barium and strontium nitrate can be so vivid. The problem with a material like copper nitrate is that it's SO hygroscopic, the moisture continues to rise even with a binder. I personally have tried nickel nitrate and strontium nitrate for a purple, using Parlon as a chlorine donor but it was too red even after several variations. and nickel nitrate is also pretty hygroscopic after some exposure (not as bad as CuNO3 however).

turbosnigel - 27-1-2012 at 17:36


I have made kilo quantities Cu(II)Bz from Potassium Benzoate and CuSO4 x 5 H2O, and it takes some serious labor and time to get it clean from the Potassium Sulfate.
My particle szise is mud-like small, so filtering is painfully slow.

My test with Amonium Perchlorate 1 + 4 (Anything more is seriously over oxidizing it, only oxidizing to as that is the ratio for burning completely to -> CO2.
Oxidizing only to CO makes the flame larger and cooler, with is both beneficial for blue color flame. (If flying trough air in the form of a star at least)

"There is no way there was any sodium ions present. Ammonium perchlorate was purchased from pyro supply."

AP is most often made from Sodium Perchlorate, so traces of Sodium is common, even if from pyrosuplier.
Less AP than you used would make it burn cooler, preventing any sodium ions present from emitting yellow.

"I thought Copper Benzoate produces blue color when mixed with Ammonium Perchlorate."
It sure does, se my Video here:

Video is of 4 different comps in a thin paper "tube" made of one ore tow layers gummed paper:

1. Water free Copper Benzoate 20% Close to theoretical amount (18%) for complete burn to CO2 with out air-oxygen.

2. Ultra pure, water free Copper salt of Terephthalic acid 25%

3. Not quite so pure Copper salt of Terephthalic acid 25%, contains Water of crystallization

4. Copper Benzoate with water of crystallization left in 20%.

Conclusion of test, leave the crystal water in fuel-salt, as it enhances color dept and flame size.

Increase amount of fule to make flame biger and burning cooler. Adding Nitrogen rich fuel such as HMTA as secondary fuel is often useful in blue flames.
But here the Copper % is already on its lowest possible concentration.

If your experimental free from diluting chrystal water, final mixture contains less then 3% Cu!
With water even less, but do not remove the water, it makes itself very useful enlarging the flame and thus the color emitting area.

The best normal firework mixtures for blue contains around 8,7% Cu, a %-number I derived from extensively averaging of the best reported formulas in the literature, and on the Internet.

Possible fix to the "yellow" blue comp of OP:

In order of importance:

1 Up CyBz to 18-25%
2 Do not remove water of crystallization, possibly meaning skipping the alcohol wash.
3 Recrystallize AP
4 Wash CuBz thorogly to remove potassium sulfat from diluting the already low Copper below useful level.

@ Aqua_Fortis_100%
"Benzoates and other benzene ring containing substances are most suited to whistling compositions rather than colouring.."

Copper Benzoate is used very successfully for a slow burning mobile blue, in "New Blue" published, in best of AFN III.

And CuBz does not contrubute to any whistling, only sodium and potassiumsalt of Bz whistle.
(I am on a quest trying to get blue whistle ;)

"Additionally, although this may not be the case but.. Was CuSO4 and water used pure enough/sodium free?"

I most successfully used aggressive 70 ppm tap water for washing and preparation, with excellent results in spherical firework shells.
But now Snail has a large expensive filter, to bring water to 0 PPM :-P

Sodium should of course be avoided, but of flame temp is correct, traces should not give OP this result?
I did filter the tecnical CuSO4 solution trougth a peace of cloth a few thimes, as it was somvwath turbid, after filtering it was sparkeling clear.

Ammonium Perchlorate and Copper Benzoate are not reacting to produce "some form of carbon benzene" They ar stabile even if wet, i have successfully rolled this to beautiful slow burning blue stars.

IIRC 23% CuBz 4% Dextrin, Primer free from KNO3!
Othervise it makes Amonium nitrate byc dubel decomposition, and things get wery wet puddle-izh... ^^
Sodium Nitrate in prime works with out this problem.
Search for: AP star prime or similar.

"whistling composition made from copper terephthalate and pure sodium-free KClO3"

I am going to make use of Tereftelate to make blue whistle rocket, i have some formula

based on KCLO4 but it needs a lot of work before i am satisfied. Thanks for sharing the KCLO3 piece of information.

To little free chlorine, to much carbon is the likely source of yelow in that comp in Aqua_Fortis KCLO3 tested.
That is a major obstacle to owercome, but it can be done.

If book mentions Paris Green but not Copper Benzoate, its be course it has not been "phased in" yet :-P
Paris Green is phased out and possible replacement is the Tereftelate or Benzoate :)

"I've always believed this sort of confines everything intimately and restricts the available atmospheric oxygen"

That is actual pretty important! If making stars that fly trough the air, 82%AP 18%CuBz is much to over oxidized. Wind speed makes available oxygen from air non trivalent.

A mixture that burns white hot stationary can make wonderful blue, when cooled by wind speed and properly oxygen balanced for this mode of operation.


Copper / AP problem is mostly present when dry, weary fine powder AP are mixed with catalysts and heated.
Avoid all adition of metall powders! As the mixture will react spontaneously and heating up, emitting Ammonia.
Larger batches vith magnesium would likely ignite if suficiently moisture or time is present.
Witout metalls, it is perfectly safe, see
"New Blue" firework composition.

And making the mixture more intimate than necessary only increase heat destroying the sensitive blue emitting CuCl in the flame. So do not mix to good and it might work :)

Crystal water in CuBZ would be best removed totally, the mixture intimately mixed in a ballmill and microporosyty introdyzed in the form of carbon.

Not att all used to writing this strange language of yours ;-)

Did i mention i now have 50 liters of home made concentrated Ammonium Tereftelate (coresponding to 10 kilos of the pure acid), waiting for me to make Ba, Cu, & Sr salts! :D

(Thanks to for the published route from PET, it sure works scaling up to "barrel size" :cool:

Will possibly Co persipitated with the bensoate, to get the amount of metal ion / fuel optimal ;)

Free snow to everyone who read all this! :D
Pick yours up here in Sweden, Limited time offer! ;)
The damn white is all ower the place, this is seriously stopping science, making the Intherblarg the only way to get the nightly fix of madsci, as you might have noticed ^^


[Edited on 28-1-2012 by turbosnigel]

jamit - 27-1-2012 at 23:32


Much appreciated for taking the time to explain it all. As a result of what you wrote, i'm going to
1. increase the benzoate composition to between 18-25% of the overall total weight,
2. I will thoroughly wash my copper benzoate which is currently being dried -- but still somewhat wet -- with cold tap water, another 10 times before setting it out to dry.
3. Recrystallize the pyro supply of AP.

thank you for that video on youtube -- the blue color was quite amazing.

So it seems that I should put the mixture of AP and Copper Benzoate into a tube if i want to see a strong blue rather than setting the loose powder on fire. I'm going to try that as soon as the copper benzoate is dry -- next week.
Again, thanks alot!!:D:D

[Edited on 28-1-2012 by jamit]

turbosnigel - 28-1-2012 at 19:54

"Much appreciated for taking the time to explain it all."

I have not explained it all, calculations is missing, i fix ;)

There are two types of Copper benzoate, Anhydrous (Gray-ish) and Mono-hydrate (Sky-blue-ish).

To simplify, there are two standard ways to balance a combustion in pyrotechnics.

1. Every carbon burns completely to CO2.
This often gives most heat per gram composition.

2. All carbon burns to CO.
This gives a greater volume of gases and lover energy per gram of composition.

This gives us 4 combinations of theoretical compositions, so lets compare the numbers for them.

We can then get the theoretical amount of fuel in each composition, usually the only calculation done.

But I figured we can also calculate Cu content, so lets do that also.

It would also be interesting to determine the relative volume of the flame.
So I invented RFS, Relative Flame volume :)
RFV is calculated by taking the number of moles of product assumed to be a gas in the flame, and divide this by how many kilos of composition the balanced composition uses.

So I went along and did the proposed calculations, and here are the result:

CuBz, water free, Burning to CO2
62 NH4ClO4 + 10 C14H10CuO4 = 148 H2O + 52 HCl + 140 CO + 31 N2 + 10 CuCl
AP 7284,38g + CuBz 3057,73g = 10342,11g
Composition uses 29,57% CuBz, and contains 6,14 mass% Cu.

Number of Moles product 381
RFV (Mol gas per kilo composition) 36,84

CuBz, water free, Burning to CO
118 NH4ClO4 + 10 C14H10CuO4 = 232 H2O + 108 HCl + 140 CO2 + 59 N2 + 10 CuCl
AP 13863,82g + CuBz 3057,73g = 16921,55g
Composition uses 18,07% CuBz and containing 3,75 mass % Cu.

Number of Moles product 549
RFV (Mol gas per kilo composition) 32,44

CuBz, mono hydrate to CO2
118 NH4ClO4 + 10 C14H10CuO4*H2O = 242 H2O + 108 HCl + 140 CO2 + 59 N2 + 10 CuCl
AP 13863,82g + CuBz*H2O 3237,73g = 17101,55g
Composition contains 18,93% CuBz*H2O, and contains 3,72 Mass % Cu.

Number of Moles product 559
RFV (Mol gas per kilo composition) 32,69

CuBz, mono hydrate to CO
62 NH4ClO4 + 10 C14H10CuO4*H2O = 158 H2O + 52 HCl + 140 CO + 31 N2 + 10 CuCl
AP 7284,38g + CuBz*H2O 3237,73g = 10522,11g
Composition contains 30,77% CuBz*H2O and contains 6,04% Cu.

Number of Moles product 391
RFV (Mol gas per kilo composition) 37,16

As a basis of the above calculations was:

Copper benzoate (Anhydrus gray-ish)

Formula C14H10CuO4, 305,7728 g/mol Found at wikipedia

20.78% Mass% Cu (Found by using molecular Weight Calculator @

Copper benzoate (Monohydrate, hevenley-blue-ish)

Formula, C14H10CuO4*H2O, 323,7728 g/mol

Based on experimental observation and Wikipedia article mentions CuBz adopts similar structure as Cu(II)Acetate, and that has

one water molecule as ligand per Copper atom is present in the so called "Chinese lantern" -structure.
We knowe the amount of water as ligand.

This gives 19.63 Mass% Cu

Ammonium Perchlorate, Formula NH4ClO4, 117.49 g/mol
- Found @ corresponding Wikipedia article

For the calculations the "ONLINE BALANCER" was used for the balance of the chemical equations.

The ligand is replaceble, so it might have been replaced by Isopropyl alcohol ? ^^

That would explain the yellow you experienced, as the carbon content would go way up!
Can alcohol act as ligand? I do not knowe if that is even possibility? Some one else that are more knowledgeable has to help us with that part.

Any solid particles in the flame, would emit gray body radiation as yellow light, Could have come from anti caking agent from some, or all of your chemicals. Dissolve and filter a small sample of each Potassium Benzoate, Copper Sulfate, And Ammonium Perchlorate and look for residue on the filter, ther shuld be none.

3. Recrystallize the pyro supply of AP.
Burn a small sample of only AP, to check for Sodium? :)

thank you for that video on youtube -- the blue color was quite amazing.

It looks ewen better in a 2" hard break, low hight, round shell, with 50 stars ;)

So it seems that I should put the mixture of AP and Copper Benzoate into a tube if i want to see a strong blue rather than setting the loose powder on fire.

Paper contains carbon, so be careful not to use to much paper.

Ohh, and the CuBz is based on a benzen ring, thus contains a shitload of energy, so stars and tub diameters shuld be kept small, otherwise the to high temperature will wash out all blue. Cooling the stars by shooting trough air helps, making stars that looks white stationary become nice blue in the sky.

Good luck


[Edited on 29-1-2012 by turbosnigel]